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The antiwear properties of tribofilms formed on steel surfaces lubricated with various multi-component lubricants were investigated at an elevated temperature and under load-speed conditions conducive to sliding in the boundary lubrication regime. The lubricants contained base oil, reduced-level (secondary) zinc dialkyl dithiophosphate (ZDDP), and nitrogenous dispersant. The wear resistance of the tribofilms produced from different oil blends was evaluated in the context of the rate of change in the sliding track volume (wear rate for material loss) and the load-bearing capacity, chemical composition, and thickness of the tribofilms. Surface profilometry and scanning electron microscopy were used to quantify the wear performance and detect the prevailing wear mechanisms, whereas X-ray photoelectron spectroscopy elucidated the chemical composition and thickness of the tribofilms. The oil blends without ZDDP did not produce tribofilms with adequate antiwear properties, whereas the oil blends containing ZDDP and dispersant generated tribofilms with antiwear characteristics comparable to those of tribofilms produced from blends with a higher ZDDP content. Although dispersants can suspend oil contaminants and preserve the cleanness of the sliding surfaces, it was found that they can also reduce the antiwear efficacy of ZDDP. This was attributed to an additive-dispersant antagonistic behavior for surface adsorption sites affecting tribofilm chemistry and mechanical properties. Among the blends containing a mixture of ZDDP and dispersant, the best antiwear properties were demonstrated by the tribofilm produced from the blend consisting of base oil, 0.05 wt% ZDDP, and a bis-succinimide dispersant treated with ethylene carbonate. The findings of this investigation demonstrate the potential of multi-component lubricants with reduced-content ZDDP and nitrogen-based dispersant to form effective antiwear tribofilms.

Variations in the microstructure and the dominant fretting wear mechanisms of carbon steel alloy in oscillatory sliding contact against stainless steel in a dry atmosphere were evaluated by various mechanical testing and microanalytical methods. These included scanning electron microscopy and energy dispersive spectrometry with corresponding elemental maps of the wear tracks, in conjunction with cross-sectional transmission electron microscopy of samples prepared by focused ion beam machining to assess subsurface and through-thickness changes in microstructure, all as a function of applied load and sliding time. Heavily dislocated layered microstructures were observed below the wear tracks to vary with both the load and sliding time. During the accumulation of fretting cycles, the subsurface microstructure evolved into stable dislocation cells with cell walls aligned parallel to the surface and the sliding direction. The thickness of the damaged subsurface region increased with the load, consistent with the depth distribution of the maximum shear stress. The primary surface oxide evolved as Fe2O3 and Fe3O4 with increasing sliding time, leading to the formation of a uniform oxide scale at the sliding surface. It is possible that the development of the dislocation cell structure in the subsurface also enhanced oxidation by pipe diffusion along dislocation cores. The results of this study reveal complex phase changes affecting the wear resistance of steels undergoing fretting wear, which involve a synergy between oxidative wear, crack initiation, and crack growth along dislocation cell walls due to the high strains accumulating under high loads and/or prolonged surface sliding.

As the demand for biobased lubricating oils continues to rise, there is a growing focus on exploring diverse oil types. Particularly noteworthy is the surge in demand for high oleic oils, which offer enhanced stability, and a richer oleic acid content compared to their regular oil counterparts. However, the performance of high oleic soybean oil (HOSO) with additives compared to regular soybean oil (RSO), remains unclear. This study is focused on revealing the compatibility of both regular soybean oil (RSO) and high oleic soybean oil (HOSO) with select antiwear and antioxidant additives, specifically zinc dialkyl dithiophosphate (ZDDP), and zinc dialkyl dithiocarbamate (ZDDC) combined with antimony dialkyldithiocarbamate (ADDC), along with a comparative performance analysis of these additives. Reciprocating friction, wear, and electrical contact resistance-based analyses were conducted to evaluate additive compatibility and wear mechanisms at room temperature lubrication conditions. Interestingly, it was observed that for the select additives, the compatibility with regular soybean oil (RSO) was better than that of high oleic soybean oil (HOSO). RSO with additives showed around 28% reduction of wear volume whereas, it was only 8% for HOSO with additives. Additional physiochemical property analyses were conducted on the lubricants to correlate the observed tribological behavior. The worn-out surfaces of the test samples were characterized thoroughly to reveal the dominant wear mechanisms. [ABSTRACT FROM AUTHOR]

A lead-free Ni–B–W (ENB-W) coating deposited by electroless method was investigated in present work. Heat-treated ENB-W coating (450 °C for 3 h) were exposed to tribological tests within a range of parameters, including load (10–50 N), speed (0.5–1.5 m/s), and distance (400–1000 m). Prior to tests, coated specimens before and after heat-treated condition were characterized. The typical globular morphology and crystalline nature was seen. The hardness, scratch hardness and first critical load of failure improved in heat treated condition. To optimize wear rate and coefficient of friction (COF), an approach has been introduced, i.e., integration of an artificial neural network (ANN) with a genetic algorithm (GA). The ANN model yielded a mean absolute percentage error of 8.4421% for predicting wear rate and 2.4138% for predicting COF. Pareto front analysis identified the optimal operating conditions as load of 34.2099 N, speed of 0.5006 m/s, and distance of 726.7243 m, resulting in both a minimum wear rate of 0.1003 × 10−8 g N−1 m−1 and a COF of 0.2099. In addition to optimization, the study also involved the characterization of the wear mechanisms of the coatings to gain a deeper understanding of their tribological behaviour. Different wear mechanisms were seen at different range of the parameters. The wear rate and COF did not vary significantly with sliding distance except at 10 N load. In fact, the wear rate was lower at 30 N and 50 N compared to 10 N. [ABSTRACT FROM AUTHOR]

The incorporation of lubricating filler can improve the self-lubricating properties of polymers and mitigate friction-induced vibration under harsh conditions. However, filler performances significantly vary depending on its size. In this study, molybdenum bisulfide (MoS2) particles of various sizes were utilized as lubricating additives to reinforce thermoplastic polyurethane (TPU). The results showed that an appropriate decrease in the particle size of MoS2 facilitated more efficient stress transfer from the polymer to the particle due to strengthened interfacial interaction, resulting in improved mechanical properties of the reinforced TPU composites. Additionally, the adsorption property of the MoS2 particle improved, extending the duration of the MoS2 tribofilm. These beneficial phenomena endow TPU composites with excellent tribological and frictional vibration reduction properties, with the 500 nm MoS2 presenting the best reinforcing effect. However, further reduction in particle size caused particle agglomeration, which adversely affected the mechanical and self-lubricating properties of the composite and eventually reduced the frictional vibration reduction properties. The findings obtained herein provide a valuable reference for developing a novel polymer with excellent friction and vibration reduction properties. [ABSTRACT FROM AUTHOR]

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Tool wear in machining is inevitable, and determining the precise moment to change the tool is challenging, as the tool transitions from the steady wear phase to the rapid wear phase, where wear accelerates significantly. If the tool is not replaced correctly, it can result in poor machining performance. On the other hand, changing the tool too early can lead to unnecessary downtime and increased tooling costs. This makes it critical to closely monitor tool wear and utilize predictive maintenance strategies, such as tool condition monitoring systems, to optimize tool life and maintain machining efficiency. Acoustic emission (AE) is a widely used technique for indirect monitoring. This study investigated the use of Short-Time Fourier Transform (STFT) for real-time monitoring of tool wear in machining AISI 4340 steel using carbide tools. The research aimed to identify specific wear mechanisms, such as abrasive and adhesive ones, through AE signals, providing deeper insights into the temporal evolution of these phenomena. Machining tests were conducted at various cutting speeds, feed rates, and depths of cut, utilizing uncoated and AlCrN-coated carbide tools. AE signals were acquired and analyzed using STFT to isolate wear-related signals from those associated with material deformation. The results showed that STFT effectively identified key frequencies related to wear, such as abrasive between 200 and 1000 kHz and crack propagation between 350 and 550 kHz, enabling a precise characterization of wear mechanisms. Comparative analysis of uncoated and coated tools revealed that AlCrN coatings reduced tool wear extending tool life, demonstrating superior performance in severe cutting conditions. The findings highlight the potential of STFT as a robust tool for monitoring tool wear in machining operations, offering valuable information to optimize tool maintenance and enhance machining efficiency. [ABSTRACT FROM AUTHOR]

The digital light processing (DLP) is one of the additive manufacturing methods, renowned for its precision and efficiency, with wide-ranging applications, notably in dentistry. Recent advancements in photocurable resins and DLP technologies have profoundly influenced dentistry. Despite their common clinical use, some resins lack comprehensive empirical studies on their mechanical and wear properties. In addition, analyzing the wear resistance of dental materials manufactured via additive manufacturing is imperative for ensuring their prolonged durability and dependability within authentic oral settings. Profound comprehension of the manner in which these materials withstand abrasive forces ensures their capability to withstand the mechanical strains imposed by chewing and brushing activities, thereby preserving their structural robustness and functional efficacy. The aims of this research are to investigate the effect of DLP process parameter setting, including: layer thickness, exposure time, and light intensity, on the wear resistance of acrylate dental materials. Using a pin-on-disc apparatus, wear tests were conducted. A steel pin, with a diameter of 5 mm, moved linearly over the specimen surface under the speed of 15 m/min and applying a force of 20 N. Scanning electron microscopy (SEM) was employed to examine the worn surface and wear mechanisms. Additionally, Analysis of Variance (ANOVA) was utilized to assess parameter effects and correlations. The findings indicate that parameter configurations exert a considerable influence on wear resistance and represent a cost-effective avenue for enhancing the wear resistance of components produced through additive manufacturing. The results revealed a direct correlation between resin curing and wear resistance, with inadequate or excessive curing leading to increased wear rates. The samples with a layer thickness of 25 µm, exposure time of 7.2 s, and light intensity of 160 W/m2, exhibited the lowest wear rate (11 × 10−2 mm3/min). Conversely, samples with a layer thickness of 100 µm, exposure time of 2.8 s and light intensity of 160 W/m2, demonstrated the highest wear rate (55 × 10−2 mm3/min). Additionally, the analysis of variance confirmed correlations between parameters, noting a negative correlation between intensity and time parameters, and positive correlations among other inter-parameter correlations. [ABSTRACT FROM AUTHOR]

An investigation of the interaction between multidimensional nano-additives and tribofilms is crucial for enhancing mechanical efficiency, extending equipment lifespan, and reducing environmental impacts. Improved tribofilm performance is obtained via several mechanisms: filling surface defects with 0D nano-additives, directional lubrication for 1D nano-additives, interlayer slippage for 2D nano-additives, and improved film durability for 3D nano-additives. Under dry lubrication, the formation of tribofilms via mechanical mixing is influenced by material hardness, surface roughness, and frictional conditions, with their thicknesses increasing by 20–30% under high loading. Conversely, liquid-lubricated films result from the physical adsorption and chemical reactions of the lubricants, with extremely high pressure additives reducing the friction coefficient by 30–50% at high pressure. A greater understanding of these mechanisms is beneficial for optimizing industrial technologies and developing efficient, eco-friendly lubrication systems. [ABSTRACT FROM AUTHOR]

Nickel-based superalloy GH4169 has gained significant prominence in aerospace and power-generation sectors due to its exceptional resistance to fatigue, creep and corrosion at high temperatures. However, wear on the contact surface remains a concern during its operational lifespan, as it can lead to crack initiation and reduce the service life of the alloy. Therefore, this study aims to comprehensively investigate the dry-sliding wear behaviors of the GH4169 superalloy under various conditions, including temperatures, applied loads and sliding speeds via a ball-on-disc tribometer. The results obtained from the study indicate that the wear rate of the GH4169 superalloy is initially high at room temperature. However, as the temperature increases to 525 °C, the wear rate significantly decreases. Subsequently, with further temperature increase to 650 °C, there is a slight rise in the wear rate. However, the findings regarding the friction coefficient present a conflicting trend compared to the wear rate. Under the same testing conditions, the wear rate of the GH4169 superalloy at 525 °C and 650 °C demonstrates a significant reduction of 21% (0.0774 × 10–4 mm3/N.m) and 19% (0.0785 × 10–4 mm3/N.m), respectively; when compared to room temperature (0.0935 × 10–4 mm3/N.m). Besides, at room temperature, the wear track depths measure approximately 34 ± 2 µm and 55 ± 3 µm for applied loads of 20 N and 60 N, respectively. These values indicate a significant wear depth under ambient temperature conditions. On the other hand, at 525 °C, the wear track depths are slightly lower compared to those at RT. The measured depths at 525 °C amount to approximately 25 ± 2 µm and 38 ± 2 µm for applied loads of 20 N and 60 N, respectively. At high temperatures and low applied loads, the wear mechanism of the GH4169 superalloy is mainly abrasion. However, at low temperatures and high applied loads, the wear mechanism becomes more complex, involving abrasion as well as oxidation, delamination, softening and melting. This study offers valuable insights into how different wear testing parameters impact the tribological characteristics of the GH4169 superalloy. [ABSTRACT FROM AUTHOR]

In this study, the effects of surface treatment namely electro-pulsing followed by laser shock peening (EP-LSP) on wear resistance properties of Ti–6Al–4V alloy are investigated. It was compared with samples treated solely with laser shock peening (LSP) and electro-pulsing treatment (EP) to investigate the effects of different processes on the friction and wear properties of Ti–6Al–4V alloy. In addition, the friction coefficient, wear rate, wear morphology were also investigated. Finally, the wear mechanism was described in detail. The results demonstrated a significant reduction in grain size for the samples after EP-1-LSP treatments. Furthermore, compared with the as-received samples, the maximum hardness of EP-1, LSP and EP-1-LSP treated samples increased by 6.5%, 5.9%, and 19.6%, respectively, and the compressive residual stress on the surface increased by 2.4%, 15.0%, and 37.2%, respectively. Under the same friction conditions, the depth of wear scar of the samples after EP-1, LSP, and EP-1-LSP treatments decreased by 7.2%, 10.6%, and 18.5% than that of the as-received sample. The as-received samples mainly exhibited severe oxidative and adhesive wear, and the LSP and EP-1 treated samples showed slight adhesive and oxidative wear. The EP-1-LSP treated samples predominantly showed signs of abrasive wear.

Transparent yttrium aluminum garnet (YAG) exhibits high hardness and abrasive resistance, making it a promising candidate for applications involving material contact, such as protective optical elements, windows, domes, and armors. When transparent YAG is employed in such applications, it may be susceptible to degradation due to friction, chemical exposure, or thermal stress. Despite its potential, there is limited research on the tribological behavior of transparent YAG. In the present study, transparent YAG ceramics were fabricated by reaction sintering of high‐purity Al2O3 and Y2O3 powders. The transparent YAG specimens had an average grain size of 20 ± 6 µm and hardness of 1068.98 ± 115.15 HV, and fracture toughness of 1.27 ± .06 MPa.m0.5. The effect of load variation from 5 to 15 N on the tribological behavior of transparent YAG was investigated when slid against chrome steel (100Cr6) balls with a hardness of 815 ± 75 HV. The low coefficient of friction (COF) and wear rate were observed due to the wedge formation (fish‐scale‐like pattern) at the surface when the load was increased from 5 to 10 N. Moreover, tribochemical layer formation, fracture, and material transfer were observed when the load was increased from 10 to 15 N, leading to high COF and increased wear rate. [ABSTRACT FROM AUTHOR]

Titanium (Ti) alloys have been widely used in biomedical applications due to their superior mechanical, physical, and surface properties, while improving their tribological properties is critical to widening their biomedical applications in the current era. The present review examines the recent progress made in enhancing the tribological performance of titanium alloys and titanium matrix composites for biomedical purposes. It specifically focuses on the progress made in biomedical coatings, mechanical surface treatment, and developing titanium matrix composites in terms of their processing, tribological testing conditions, and characterization. Despite thorough investigations, the specific testing procedures for evaluating the friction and wear properties of the alloy and/or biomedical component are still uncertain. The majority of researchers have selected test methods and parameters based on previous studies or their own knowledge, but there is a scarcity of studies that incorporate limb-specific tribological tests that consider the distinct kinematic and biological structure of human limbs. Since advanced microscopy has great potential in this field, a variety of advanced characterization techniques have been used to reveal the relationship between microstructural and tribological properties. Many coating-based strategies have been developed using anodizing, PEO, VD, PVD, nitriding, thermal spray, sol-gel, and laser cladding, however; composition and processing parameters are crucial to improving tribological behaviour. Reinforcing component type, amount, and distribution has dominated Ti matrix composite research. Ti grade 2 and Ti6Al4V alloy has been the most widely used matrix, while various reinforcements, including TiC, Al2O3, TiB, hydroxyapatite, Si3N4, NbC, ZrO2 have been incorporated to enhance tribological performance of Ti matrix. Mechanical surface treatments improve biomedical Ti alloys' tribological performance, which is advantageous due to their ease of application. The implementation of machine learning methods, such as artificial neural networks, regression, and fuzzy logic, is anticipated to make a substantial contribution to the field due to their ability to provide cost-effective and accurate results. The microstructural and surface features of biomedical Ti alloys directly affect their tribological properties, so image processing strategies using deep learning can help researchers optimize these properties for optimal performance. [ABSTRACT FROM AUTHOR]

The spacer layer imaging method (SLIM) is widely used to measure the thickness of additive and lubricant films, in lubricant development and evaluation, and for fundamental research into elastohydrodynamic lubrication and tribofilm formation mechanisms. The film thickness measurement, as implemented on several popular tribometers, provides powerful, non-destructive in-situ mapping of film topography with nanometre-scale height sensitivity. However, the results can be highly sensitive to experimental procedure, machine condition, and image analysis, in some cases reporting unphysical film thickness trends. The prevailing image analysis techniques make it challenging to interrogate these errors, often hiding their multivariate nonlinear behaviour from the user by spatial averaging. Herein, several common ‘silent errors’ in the SLIM measurement, including colour matching to incorrect fringe orders, and colour drift due to the optical properties of the system or film itself, are discussed, with examples. A robust suite of novel a priori and a posteriori methods to address these issues, and to improve the accuracy and reliability of the measurement, are also presented, including a novel, computationally inexpensive circle-finding algorithm for automated image processing. In combination, these methods allow reliable mapping of films up to at least 800 nm in thickness, representing a significant milestone for the utility of SLIM applied to elastohydrodynamic contact. [ABSTRACT FROM AUTHOR]

The service performance of polycrystalline cubic boron nitride (PcBN) tools undergoes significant changes due to the deep space environment to the structure and wear behaviors of PcBN. In this paper, the effect of cryogenic treatment (CT) was studied to investigate the physical and tribological behaviors of PcBN. The hardness and wear resistance of PcBN are improved but wear forms are not affected, which are abrasive wear. The shedding of cBN played the role of micro-cutting edges, carving furrows on surfaces. As the CT duration increases, the wear rate of PcBN decreases from 2.56 × 10−8 mm3/N mm to 1.61 × 10−8 mm3/N mm for sliding against Si 3 N 4. When PcBN slid Al 2 O 3 , the lowest wear rate is 1 × 10−8 mm3/N mm which the decline reached 34 %. Due to discrepancies in physical and mechanical properties, Si 3 N 4 and YG8 balls exhibit abrasive and adhesive wear, and Al 2 O 3 shows fatigue wear. Until the fatigue failure appeared, Al 2 O 3 exhibited the lowest wear rate of 2.30 × 10−9 mm3/N mm. Among three materials, the wear rate of Si 3 N 4 was the highest. By calculating the wear rate ratio of the materials, it was concluded that the optimal removal efficiency was achieved for Si 3 N 4 and YG8 when CT duration is 24 and 48 h, respectively. [ABSTRACT FROM AUTHOR]

This study investigates the impact of temperature on the tribological performance of duplex layer CrN/DLC and nano-multilayers DLC-W coatings deposited using hybrid PVD-PECVD techniques on carburized and hardened 16MnCr5 discs cut from internal combustion engines valve tappets. Reciprocating dry sliding experiments were conducted at 25 °C, 150 °C, 200 °C, and 250 °C to analyze the high-temperature tribological behavior of the coatings. The wear mechanisms were characterized using SEM, EDS mapping, Raman spectroscopy, and nanoindentation. The lowest coefficient of friction was obtained for CrN/DLC at 25 °C. The CrN/DLC coefficients of friction (COF) increase with temperatures due to increasing adhesive wear. Similarly, DLC-W exhibited a comparable trend with increasing temperature from 25 °C to 250 °C. Both coatings' wear resistance decreased with higher temperatures due to the transformation of sp3 C bonds to sp2 C bonds, facilitating the plastic deformation of the coatings and afterward of the substrate. The CrN/DLC displayed superior wear resistance to the DLC-W coating across all temperatures. The DLC-W multilayer coating showed poor wear resistance above 150 °C, being completely removed during the testing. Compared to both coatings, the uncoated 16MnCr5 discs exhibited higher coefficients of friction and wear rates at all temperatures. Predominant wear mechanisms observed in the coated discs were adhesive and abrasive. The study revealed a decrease in the coatings' structural and mechanical properties with rising temperatures. Hard abrasive WC particles were identified as contributing to increased wear rates in the multilayer DLC-W coatings. [ABSTRACT FROM AUTHOR]

American iron and steel institute (AISI) P20 steel, commonly used in plastic mold production, frequently faces significant wear challenges during service. Industries continually seek efficient and cost‐effective solutions to mitigate these issues. Herein, heat‐treatment and sol‐enhanced NiB–TiO2 coating are applied separately or in combination to exclusively assess the wear resistance improvement of as‐received P20 steel. To this end, wear tests are conducted under different loads using a pin‐on‐disk test, and the worn surfaces are evaluated through a laser scanning microscope, scanning electron microscopy (SEM), and energy‐dispersive spectroscopy (EDS). In the findings, it is revealed that the heat treatment significantly enhances the wear resistance of AISI P20 steel, reducing the wear rate by almost half due to microstructure modification and surface hardening. In addition, NiB–TiO2 coating provides further enhancement of wear endurance. It seems to be sufficient to provide excellent wear resistance to steel since the wear rate decreases by approximately 61% and 65% when the coating is applied to the as‐received and heat‐treated P20, respectively. Based on SEM–EDS analysis, the wear mechanism of steel is similar for both steel conditions, involving abrasive wear and delamination. However, the NiB–TiO2 coating intensively modifies the wear mechanism of the steel, leading to a combination of abrasive, adhesive, and fatigue wear. [ABSTRACT FROM AUTHOR]

Tribological characteristics of fine-grained dual-phase high-entropy carbide/boride ceramics were investigated using the ball-on-flat dry sliding method in air, applying linear reciprocation motion with SiC counterpart. Detailed fractographical analyses were used for the characterization of the deformation and damage mechanisms. The investigated system with composition (Ti 0.14 Zr 0.2 Nb 0.2 Hf 0.2 Ta 0.26)C + (Ti 0.38 Zr 0.18 Nb 0.22 Hf 0.115 Ta 0.105)B 2 showed density with value 8.72 g/cm3 and very high hardness of HV1 29.4 ± 2.0 GPa. The friction coefficient at the test with 5 N was 0.56 and during the test with 10 N and 25 N loads were 0.48 and 0.5, respectively. The effective wear rates at the loads of 5 N and 25 N were very similar with values of 7.93 × 10−7 mm3/Nm and 6.63 × 10−7 mm3/Nm. At load 50 N the effective wear rate is significantly higher with a value of 9.11 × 10−6 mm3/Nm. Detailed fractography revealed that the dominant wear mechanisms at loads of 5 N and 25 N were an oxidation-driven tribochemical reaction and tribo-layer formation in boride grains and mechanical wear in carbide grains and at the load of 50 N fracture of boride and carbide grains and formation of chemically complex tribolayers. [ABSTRACT FROM AUTHOR]

In this study, the wear characteristics of the die were tested and analyzed through compaction tests, and the distribution of wear depth along the direction toward the extrusion outlet was obtained. A discrete element method (DEM) model of the die's wear process was established. The results show that the severe wear area is located near the stop position of the compression rod, forming a plow-shaped wear area along the extrusion direction, accompanied by fatigue peeling. The wear depth gradually decreases towards the extrusion outlet. The DEM model partially reveals the occurrence of the wear phenomenon, but the particle motion speed deviates from the actual situation. The maximum compression force value range during the DEM compression stage is within the actual maximum compression force value range, and the relative error range of the average maximum compression force is less than 2%. By verifying the formula to calibrate the model, the calibrated model is compared with the actual mold wear, and the predicted value is close to the actual test result. The DEM can be used to explore the wear mechanism and predict the die's wear failure process, laying the foundation for optimizing die wear resistance design. [ABSTRACT FROM AUTHOR]

Identification of changes occurring on the working surface of lubricated gears using analytical equipment, e.g., an FE-SEM scanning electron microscope with an EDS microanalyzer, a WLI interferometric microscope, or a GDEOS optical discharge spectrometer, enables the characterisation of wear mechanisms of this surface. Definition of the phenomena occurring on the surface of tribo-couples after scuffing tests enables a comparative analysis of scuffing resistance and surface properties of the micro- and nanostructure, and elemental composition of the tested gears. Recognition and analysis of the wear mechanisms occurring on the working surface of gears will reduce the risk of damage and losses resulting from the need for maintenance and repair. The study concerned the working surfaces of gears made of 17HNM and 35HGSA steels on which a W-DLC/CrN coating was deposited. Shell Omala S4 GX 320 commercial industrial oil with a synthetic PAO (polyalphaolefin) base was selected for the lubrication of the gears. Tribological tests employed an FZG gear scuffing under severe conditions test method and they were carried out on a T-12U test rig for cylindrical gear analysis. [ABSTRACT FROM AUTHOR]

Herein, MoS2 solid lubricant is introduced in the form of Mo‐coated MoS2 powder, to enhance the antifriction properties of sintered ferrous antifriction materials (FAMs). The microstructure, phase composition, and tribological properties of Fe–15Cu–0.8C–3.75 (Mo‐coated MoS2) (MC1) are investigated and compared with Fe–15Cu–0.8C (M0) samples, with a discussion on the wear mechanism at a wide temperature range of room temperature to 600 °C. The study reveals that the addition of Mo‐coated MoS2 powders effectively prevents the decomposition of MoS2 during sintering, enhances the bonding strength between MoS2 and the substrate, and significantly improves the hardness of the sintered Fe–15Cu–0.8C samples. In comparison with the sintered Fe–15Cu–0.8C samples, the sintered Fe–15Cu–0.8C–3.75 (Mo‐coated MoS2) samples exhibit good antifriction properties with a frictional coefficient of 0.23 at 600 °C and a wear rate of 6.3 × 10−7mm3 N m−1 at 300 °C. Introducing Mo‐coated MoS2 significantly reduces the average friction coefficient and wear rate of the sintered FAMs at elevated temperatures, attributed to the formation of FeMoO4. The antifriction performance of MC1 samples notably decreases with increasing test temperatures. The main wear mechanism is oxidative wear above 300 °C. [ABSTRACT FROM AUTHOR]

Wear behavior of a fine‐grained dual‐phase high‐entropy carbide/boride ceramics was investigated using ball‐on‐flat dry sliding methods in air, applying rotational and linear reciprocation motion with SiC counterpart. The investigated system showed very high nanohardness of the carbide and boride grains with mean values of 37.4 ± 2.3 and 43.0 ± 2.9 GPa, respectively, with the microhardness of dual system HV1 29.4 ± 2.0 GPa. The stabilized friction coefficient values during the circular tests changing from.62 to.77. During the reciprocal test, the frictional coefficient values are very similar with an average value of.53. The specific wear rates during the circular motion were similar in the range from 4.65 × 10−7 to 1.68 × 10−7 mm3/N m. During the reciprocal test, the wear rates at 5 and 25 N were similar as in the case of circular motion, but at 50 N load, the wear rate increased significantly to the value of 9.11 × 10−6 mm3/N m. The dominant wear mechanisms in all cases were oxidation driven tribochemical reaction and tribolayer formation in boride grains and mechanical wear in carbide grains. During the linear reciprocation test, the loading mode created conditions resulted in relatively low coefficient of friction and very high specific wear rate. [ABSTRACT FROM AUTHOR]

This study investigates the tribological behaviour of Al-20Mg2Si composite having potential applications in automobiles. A pin-on-disc apparatus was employed to assess its performance under diverse operating conditions relevant to automotive components. These conditions encompassed variations in sliding conditions (dry and lubricated), temperatures (ranging from 30°C to 200°C), and loads (20N, 40N, and 60N), with a focus on understanding their influence on wear characteristics, mechanisms, wear maps, and surface topography. The findings emphasize the pronounced impact of test conditions on wear properties. Dry sliding conditions showed a substantial increase in both cumulative wear and friction coefficient, rising by 13.17 and 1.47 times, respectively, from the 30°C test to the 200°C test with a 60N load. Conversely, lubrication yielded significantly lower cumulative wear and friction coefficients, measuring only 0.07 and 0.15 times those observed during room temperature dry sliding conditions. Surface roughness analysis confirmed that higher loads and temperatures resulted in increased roughness, while lubrication effectively reduced surface roughness. FESEM analysis of worn surfaces and debris revealed that under dry sliding at room temperature, the primary wear mechanism was abrasive, with secondary mechanisms being oxidative and adhesive wear. In contrast, at high temperatures during dry sliding, the primary mechanism shifted to adhesive wear, accompanied by secondary mechanisms including delamination, oxidative wear, and plastic deformation. Wear map analysis showed that at room temperature, wear changed from severe to moderate to mild as sliding distance increased. However, with increased temperature and load, wear shifted from mild to moderate to severe. [ABSTRACT FROM AUTHOR]

As the demand for biobased lubricating oils continues to rise, there is a growing focus on exploring diverse oil types. Particularly noteworthy is the surge in demand for high oleic oils, which offer enhanced stability, and a richer oleic acid content compared to their regular oil counterparts. However, the performance of high oleic soybean oil (HOSO) with additives compared to regular soybean oil (RSO), remains unclear. This study is focused on revealing the compatibility of both regular soybean oil (RSO) and high oleic soybean oil (HOSO) with select antiwear and antioxidant additives, specifically zinc dialkyl dithiophosphate (ZDDP), and zinc dialkyl dithiocarbamate (ZDDC) combined with antimony dialkyldithiocarbamate (ADDC), along with a comparative performance analysis of these additives. Reciprocating friction, wear, and electrical contact resistance-based analyses were conducted to evaluate additive compatibility and wear mechanisms at room temperature lubrication conditions. Interestingly, it was observed that for the select additives, the compatibility with regular soybean oil (RSO) was better than that of high oleic soybean oil (HOSO). RSO with additives showed around 28% reduction of wear volume whereas, it was only 8% for HOSO with additives. Additional physiochemical property analyses were conducted on the lubricants to correlate the observed tribological behavior. The worn-out surfaces of the test samples were characterized thoroughly to reveal the dominant wear mechanisms.

Abstract Squaring, a wood transformation process, is an operation which consists of introducing the logs into a squaring machine which then uses sharp tools to cut the wood into pieces with high surface quality. Tool steels used in this process experience significant wear, damaging the wood surface and hence leading to substantial scrape rate. This study investigates the wear resistance of three tool steels specifically designed for wood cutting applications: modified AISI A8, modified steels with 0% and 1% tungsten, and powder metallurgy prepared W360 steel. Furthermore, the influence of a PVD coating on the wear resistance of the three alloys was investigated. ASTM G65 abrasive wear tests were conducted using the dry sand/rubber wheel abrasion test. A methodology using a non-contact 3D measurement system and specialized software was developed, allowing for a thorough quantitative assessment of the wear of these steels. The results revealed that the coated A8mod + 1%W steel exhibits the best resistance among the coated steels. Despite the excellent intrinsic resistance of W360 steel, the coating did not provide a significant improvement for this steel, showing only a 10% reduction in wear. Microstructural analysis revealed that the predominant wear mechanisms were abrasion and impact. The relative performance of each steel was quantified and is reported. Field trials conducted under actual cutting conditions, indicate the superiority of W360 steel in terms of resilience to wear and impacts compared to other tested alloys, while confirming the effectiveness of surface treatments in mitigating material wear. However, A8 steel modified with 1% tungsten exhibits increased wear under coating.

The M50 bearing steel underwent a combined treatment of laser shock peening (LSP) and nitrogen ion implantation. The microstructure, surface mechanical properties and tribological behaviors were evaluated. Comparative analysis with the untreated sample revealed significant improvements in surface nano-hardness, increasing from 7.51 GPa to 11.35 GPa, 11.51 GPa, and 12.62 GPa for samples subjected to LSP, ion implantation, and combined strengthening, respectively. Correspondingly, surface compressive residual stress showed notable increases from −15.55 MPa to −1043.76 MPa, −451.34 MPa, and −1276.13 MPa, respectively. The improved surface mechanical properties observed in the combined strengthened sample are likely due to the synergistic effects of the combined strengthening. In friction tests, the combined strengthened sample exhibited the lowest friction coefficient, attributed to the presence of a metal nitride layer and a thicker amorphous layer. Wear mechanisms transitioned from fatigue spalling for the untreated specimen to slight wear and the formation of an oxidative adhesion layer after LSP and ion implantation. Remarkably, the surface of the combined strengthened specimen demonstrated minimal wear, with only an oxidative adhesion layer present.

This research studies the energy consumption and wear mechanism of carbide cutting tools in dry machining of Ti6Al4V alloy. In the first phase of experiments, full factorial design experiments were employed to study the tool wear rate (R) and specific cutting energy (SCE) with respect to the machining conditions (cutting speed and feed rate). Results showed that machining responses such as tool wear and energy consumption are affected by cutting conditions, thus requiring investigation to understand the wear mechanisms. Therefore, in the second phase, additional experiments were performed to investigate the tool-workpiece interactions at the cutting conditions reported to have low, moderate, and high tool wear. It was revealed that strong adhesion and material transfer between the tool and workpiece caused high wear. Electron dispersive X-ray spectroscopy (EDX) analysis of worn tools showed that the transfer of tungsten (W) and cobalt (Co) to the workpiece and titanium to the tool surface is the primary cause of tool deterioration. As a result, diffusion and dissolution have degraded cutting performance and weakened the tool edge, leading to rapid wear. Furthermore, worn tools resulted in relatively higher energy consumption per unit volume of material removed at the tooltip. The degradation of cutting performance and weakening of the tool edge results in rapid wear and higher energy consumption. The study suggests that minimizing tool wear is crucial for energy reduction, improved sustainability, and cleaner production goals in dry machining of titanium-based alloys. [ABSTRACT FROM AUTHOR]

Reduction of friction and wear by lubrication is necessary to improve the efficiency and prolong the lifespan of industrial machinery. However, several aspects regarding the lubrication effects in additive-combined oil are still unresolved. This study focuses on the effects of combining zinc dialkyldithiophosphate (ZnDTP), molybdenum dithiocarbamate (MoDTC), and Ca sulfonate on the frictional behavior of poly-α-olefin 4 (PAO4) lubricant oils. Ball-on-disk friction tests demonstrated that the exclusive addition of high-base Ca sulfonate solution reduced friction and wear of the lubricating oil. When combined with ZnDTP and MoDTC, the friction coefficients of PAO with high-base and low-base Ca sulfonate are affected by competitive reactions on the sliding surface. Quartz crystal microbalance with dissipation monitoring measurements suggests that high-base Ca sulfonate forms a stronger adsorption film than low-base Ca sulfonate. Atomic force microscope observations confirmed that the addition of low-base Ca sulfonate reduced friction and wear, whereas high-base Ca sulfonate induced competitive reactions with ZnDTP and MoDTC. This study provides valuable insights into the effects of the combination of additives on the lubricity of PAO and their impact on friction and wear characteristics, which are valuable for the design of suitable lubricants for industrial machinery. [ABSTRACT FROM AUTHOR]

Polytetrafluoroethylene (PTFE) has great potential for applications in water-lubricated bearings; however, in heavy load conditions at low speeds, PTFE suffers from severe friction and abrasion because of its poor wear resistance. In this study, silicon carbide (SiC) content and particle size are investigated in relation to PTFE water-lubricated composites' tribological properties. The results show that the wear resistance of PTFE composites can be significantly improved when the filling amount of SiC particles was between 3 and 5 wt.%, and the composites containing 5 wt.% SiC reduced wear loss by 99.44%. The composites' friction and wear properties decreased as SiC particle size increased, and wear mechanism for the composites shifted from adhesive to abrasive. Wear loss on PTFE composites filled with 40 nm SiC particles was reduced by 97.03%, showing the best wear resistance. This study provides an experimental basis for the development of high-performance PTFE water-lubricated bearings. [ABSTRACT FROM AUTHOR]

Squaring, a wood transformation process, is an operation which consists of introducing the logs into a squaring machine which then uses sharp tools to cut the wood into pieces with high surface quality. Tool steels used in this process experience significant wear, damaging the wood surface and hence leading to substantial scrape rate. This study investigates the wear resistance of three tool steels specifically designed for wood cutting applications: modified AISI A8, modified steels with 0% and 1% tungsten, and powder metallurgy prepared W360 steel. Furthermore, the influence of a PVD coating on the wear resistance of the three alloys was investigated. ASTM G65 abrasive wear tests were conducted using the dry sand/rubber wheel abrasion test. A methodology using a non-contact 3D measurement system and specialized software was developed, allowing for a thorough quantitative assessment of the wear of these steels. The results revealed that the coated A8mod + 1%W steel exhibits the best resistance among the coated steels. Despite the excellent intrinsic resistance of W360 steel, the coating did not provide a significant improvement for this steel, showing only a 10% reduction in wear. Microstructural analysis revealed that the predominant wear mechanisms were abrasion and impact. The relative performance of each steel was quantified and is reported. Field trials conducted under actual cutting conditions, indicate the superiority of W360 steel in terms of resilience to wear and impacts compared to other tested alloys, while confirming the effectiveness of surface treatments in mitigating material wear. However, A8 steel modified with 1% tungsten exhibits increased wear under coating. [ABSTRACT FROM AUTHOR]

Dry sliding friction and wear test of Cu/CrB2 composites manufactured by ex situ method was studied, and the mechanical properties were also measured to assistant analysis wear behaviour. When CrB2 content is 3 vol.-%, both the mechanical and tribological properties reach the maximum values, viz., 113 HV, 304 MPa and 9.1 × 10−5 mm3 N−1 m−1 of the normal load is 10 N, higher 71.2%, 33.3%, lower 52.8% than that of pure Cu, respectively, which can be ascribed to the increase of hardness and the transfer of main wear mechanisms of Cu matrix from adhesive to abrasive wear by the addition of CrB2. Further increase CrB2 content to above 5 vol.-%, wear resistance would decreases since the pulled out of CrB2 particles. [ABSTRACT FROM AUTHOR]

The NiTi alloy has attracted significant interest owing to its notable wear and corrosion resistance, suggesting the significant promise of utilizing additively manufactured NiTi alloys in tribological applications. In this study, dry sliding wear tests with sliding velocity of 0.1 m/s for total distance of 250 m at room temperature, 50 °C, 100 °C, and 200 °C were carried out on samples of NiTi alloy samples fabricated using laser powder and laser wire directed energy deposition (LP-DED and LW-DED) processes. Enhanced friction and wear behavior of LP-DED samples were captured at lower temperatures due to higher hardness and the stable dominating NiTi B2 austenite phase in the sample microstructure as confirmed from x-ray diffraction (XRD) analysis. Accumulated transferred material at lower temperatures played a crucial role in modifying the wear mechanisms. However, at higher temperatures both LP-DED and LW-DED samples presented similar wear mechanisms. [ABSTRACT FROM AUTHOR]

The present study investigates the dry sliding wear behavior of Wire arc additive manufactured (WAAM) eutectic Al-Si alloy, with a particular focus on the effects of solidification and microstructural characteristics on wear behavior. Microstructural analysis indicated that the secondary dendrite arm spacing (SDAS) for the WAAM sample was three times higher than that of the cast sample. The WAAM sample exhibited thin, long columnar dendrites, while the cast samples displayed coarse and ripened dendrites. Furthermore, EBSD analysis revealed that the WAAM sample had a higher percentage (88.6%) of low-angle grain boundaries (LAGBs), contributing to their increased strength compared to cast samples with 78.6% LAGBs. The maximum wear rate of 5.45 × 10–6 g/m was observed at a normal load of 25 N and a sliding speed of 1.1 m/s with a coefficient of friction (CoF) of 0.59 for WAAM samples while casting samples exhibited a lower wear rate of 3.06 × 10–6 g/m and a CoF of 0.55 under identical conditions. Delamination, severe adhesion, and abrasion were the primary wear mechanisms under maximum wear rate test conditions. The subsurface of WAAM samples contained a mechanical mixed layer (MML), while cast samples revealed a stable thin oxide layer. The study found that samples with higher texture strength and lower Taylor factor (TF) values were more prone to damage. [ABSTRACT FROM AUTHOR]

The ability of cryogenic treatment to improve tool steel performance is well established; however, the selection of optimal heat treatment is pivotal for cost reduction and extended tool life. This investigation delves into the influence of distinct cryogenic and tempering treatments on the hardness, fracture toughness, and tribological properties of Vanadis 6 tool steel. Emphasis was given to comprehending wear mechanisms, wear mode identification, volume loss estimation, and detailed characterization of worn surfaces through scanning electron microscopy coupled with energy dispersive spectroscopy and confocal microscopy. The findings reveal an 8–9% increase and a 3% decrease in hardness with cryogenic treatment compared to conventional treatment when tempered at 170 °C and 530 °C, respectively. Cryotreated specimens exhibit an average of 15% improved fracture toughness after tempering at 530 °C compared to conventional treatment. Notably, cryogenic treatment at −140 °C emerges as the optimum temperature for enhanced wear performance in both low- and high-temperature tempering scenarios. The identified wear mechanisms range from tribo-oxidative at lower contacting conditions to severe delaminative wear at intense contacting conditions. These results align with microstructural features, emphasizing the optimal combination of reduced retained austenite and the highest carbide population density observed in −140 °C cryogenically treated steel. [ABSTRACT FROM AUTHOR]

Aluminum matrix composites (AMCs) find extensive use across diverse industries such as automotive, aerospace, marine, and electronics, owing to their remarkable strength-to-weight ratio, corrosion resistance, and mechanical properties. However, their limited wear resistance poses a challenge for applications requiring high tribological performance. Abrasive wear emerges as the predominant form of wear encountered by AMCs in various industrial settings, prompting significant research efforts aimed at enhancing their wear resistance. Over the past decades, extensive research has investigated the influence of various reinforcements on the abrasive wear behavior of AMCs. This paper presents a comprehensive review of the impact of different variables on the wear and tribological response of aluminum composites. This review explores possible wear mechanisms across various tribosystems, providing examples drawn from the analysis of existing literature. Through detailed discussions on the effects of each variable, conclusions are drawn to offer insights into optimizing the wear performance of AMCs. [ABSTRACT FROM AUTHOR]

Modular artificial hip joints are a clinical standard today. However, the release of wear products from the head–taper interface, which includes wear particles in the nm size range, as well as metal ions, have raised concerns. Depending on the loading of such taper joints, a wide variety of different mechanisms have been found by retrieval analyses. From these, this paper concentrates on analyzing the contribution of gross slip fretting corrosion at ultra-mild wear rates using a bovine calf serum solution (BCS) as the lubricant. The parameters were chosen based on biomechanical considerations, producing wear rates of some ng/m wear path. In parallel, the evolution of tribomaterial (third bodies) was analyzed as to its constituents and generation rates. It has already been shown earlier that, by an advantageous combination of wear mechanisms and submechanisms, certain constituents of the tribomaterial remain inside the contact area and act like extreme-pressure lubricant additives. For the known wear and corrosion resistance of austenitic high-nitrogen steels (AHNSs), which outperform CoCrMo alloys even under inflammatory conditions, we hypothesized that such steels will generate ultra-mild wear rates under gross slip fretting. While testing AHNSs against commercially available biomedical-grade materials of CoCrMo and TiAlV alloys, as well as zirconia-toughened alumina (ZTA) and against itself, it was found that AHNSs in combination with a Ti6Al4V alloy generated the smallest wear rate under gross slip fretting corrosion. This paper then discusses the wear behavior on the basis of ex situ analyses of the worn surfaces as to the acting wear mechanisms and submechanisms, as well as to the tribological reaction products. [ABSTRACT FROM AUTHOR]

The tribological behavior of wheel and rail material twin-disc samples prepared under laboratory-controlled grinding operations was studied. A laboratory grinding device was designed and validated to produce similar results to those found in the field in terms of surface quality and presence of white etching layer (WEL). The test samples were evaluated in a twin-disc machine under dry and lubricated conditions. The results showed that the surface finishing parameters and the microstructure change greatly depending on the surface preparation procedure, and that such changes affect the tribological response of the samples. The wear rates of the tribological tests for the different rail surface qualities showed a reduction of 47.4% for the lubricated tests and 7.3% for the dry tests when the surfaces of the rail specimens were finished by grinding. This is only applied when the WEL thickness was less than 4 μm. [ABSTRACT FROM AUTHOR]

Zr-based bulk metallic glasses (BMGs) are promising for extensive industrial applications due to their superior mechanical properties, excellent glass formation ability (GFA), and low manufacturing costs. However, the wear resistance of Zr-based BMGs, especially when exposed to high-temperature service environments, is deficient and could lead to premature failure of critical components. Herein, we report an effective strategy that can significantly enhance the high-temperature wear resistance of Zr-based BMGs, referred to as pre-oxidation treatment (PT). At ambient temperature, the wear rate of the pristine Zr-based BMG samples was estimated to be ∼173.7 × 10−6 mm3 N−1 m−1, whereas the PT samples subjected to the PT strategy showed no detectable volume loss. In addition, the wear rate of the PT samples at 250 °C was ∼11.5 × 10−6 mm3 N−1 m−1. Intriguingly, even as the temperature surpassed the crystallization point of the BMG, the PT samples demonstrated a further enhancement in wear resistance, showcasing a wear rate of approximately ∼7.29 × 10−6 mm3 N−1 m−1. Our work introduces a promising and convenient strategy to enhance the high-temperature wear resistance of Zr-based BMG components, thereby promoting their application in real-world engineering scenarios.

Tool wear in machining is inevitable, and determining the precise moment to change the tool is challenging, as the tool transitions from the steady wear phase to the rapid wear phase, where wear accelerates significantly. If the tool is not replaced correctly, it can result in poor machining performance. On the other hand, changing the tool too early can lead to unnecessary downtime and increased tooling costs. This makes it critical to closely monitor tool wear and utilize predictive maintenance strategies, such as tool condition monitoring systems, to optimize tool life and maintain machining efficiency. Acoustic emission (AE) is a widely used technique for indirect monitoring. This study investigated the use of Short-Time Fourier Transform (STFT) for real-time monitoring of tool wear in machining AISI 4340 steel using carbide tools. The research aimed to identify specific wear mechanisms, such as abrasive and adhesive ones, through AE signals, providing deeper insights into the temporal evolution of these phenomena. Machining tests were conducted at various cutting speeds, feed rates, and depths of cut, utilizing uncoated and AlCrN-coated carbide tools. AE signals were acquired and analyzed using STFT to isolate wear-related signals from those associated with material deformation. The results showed that STFT effectively identified key frequencies related to wear, such as abrasive between 200 and 1000 kHz and crack propagation between 350 and 550 kHz, enabling a precise characterization of wear mechanisms. Comparative analysis of uncoated and coated tools revealed that AlCrN coatings reduced tool wear extending tool life, demonstrating superior performance in severe cutting conditions. The findings highlight the potential of STFT as a robust tool for monitoring tool wear in machining operations, offering valuable information to optimize tool maintenance and enhance machining efficiency.